1. Field of the Invention
The present invention relates to fasteners for assembly situations which otherwise do ot allow straightforward use of standard tools and assembly methods. More specifically, the present invention relates to apparatus for use in such a situation for holding a nut in position for assembly of a part to a workpiece where a degree of fastener float is desired.
2. Description of Related Art
Manufacturers use various methods for securing a plurality of members together in blind, semi-blind, or otherwise awkward assembly situations which do not permit a simple fastening with a nut, bolt and standard tools. For example, where access to one side of a workpiece is restricted, it may be difficult or impossible for an assembler to engage a nut on that side of the workpiece with a standard wrench or socket while simultaneously engaging the head of a bolt on the other side. Various methods have been employed to overcome this problem. For instance, a nut may be welded to one side of the workpiece so that it is unnecessary to engage the nut with a tool during assembly. However, making use of such a welded nut may prove difficult because the weldment makes no allowance for tolerances as the nut is immovable with respect to the workpiece.
Another conventional solution utilizes a cage nut, wherein a nut is retained in a cage, the cage being fixed to the workpiece. The cage allows the nut some freedom of movement with respect to the workpiece, but can be designed to limit the range of movement. The cage nut functions adequately, but the fabrication of the cage and its attachment to the workpiece represent increased cost.
An alternative way commonly used to overcome blind or awkward assembly situations involves design and employment of specialized installation and removal tools which provide access to the desired area of attachment. For instance, a wrench may be designed with a shaft bent in numerous places at desired angles, allowing an assembler to achieve simultaneous engagement of a nut and bolt. However, these specialized tools must be used every time the bolt is ever removed and reinstalled. Therefore, anyone wishing to remove the article from the workpiece must have access to the specialized tools, as the operation will likely be difficult or impossible to accomplish with standard tools.
A further known solution involves the use of conventional floating nut plates. Nut plates have been used extensively on panels and other parts, providing a means for holding a nut to the part so that it is available, while also allowing for limited floating movement of the nut so that it can be more easily engaged by a bolt. Such a fastening device typically includes a receptacle which is provided by a flat plate from which portions are bent to engage and retain flanges projecting from the nut. This holds the nut to the receptacle, while allowing movement of the nut.
The receptacle ordinarily includes an extension on either side of the nut, each having an opening for the purpose of receiving separate fasteners used in securing the receptacle to the workpiece. Normally, a rivet is received in each of these openings to provide a means for attachment. Therefore, to install the assembly on a workpiece, it is necessary to drill three accurately spaced openings through the workpiece. Two of these are for the rivets used in securing the receptacle to the workpiece. Between them is a larger opening through which the threaded shank of a bolt may pass for engaging the nut. In addition to drilling the three holes, it is then necessary to extend the rivets through the outer openings and upset them to complete the fastening sequence. This is a time-consuming and relatively expensive operation. Furthermore, the need for the extra openings for the rivets in some instances can undesirably weaken the part to which the assembly is to be attached. Removal of the assembly also takes time in requiring removal of the two rivets to permit the unit to be separated from the workpiece. The necessity of dimensioning the receptacle so as to include the two rivet holes causes it to be relatively long, so that it may not be possible to fit the assembly at corners and certain locations where spacing is limited. Special receptacle designs then are required, and these are a great deal more expensive than those of conventional construction. Inventory costs are increased by the necessity to stock different versions of the nut plate so that those having special receptacles are available as needed.
U.S. Pat. No. 3,695,324, the disclosure of which is hereby incorporated by reference, shows a floating nut assembly including a basket having upwardly extending sidewalls with slots in them which receive tabs projecting from a sleeve member having a tubular section extending through a central opening in the basket member. The nut also has tabs projecting through the slots in the sidewalls of the basket member. The assembly dimensioned so that while the tabs hold the nut to the basket member the nut is permitted to have limited floating movement. Attachment of the assembly to the workpiece is accomplished by extending the tubular section through a single opening in the workpiece. A straight knurl is provided on the tubular portion and becomes embedded in the periphery of the opening in the workpiece, which thereby prevents rotation of the assembly.
Although the floating nut assembly described in U.S. Pat. No. 3,695,324 represents a decrease in time and cost required to mount the assembly to the workpiece as compared to other conventional designs, the assembly itself is rather complex and requires multiple specially designed components, which translates to additional expense.